MXPA96002794A - Sieves for paperwork machines, filters and reinforcement fabrics for elastomers, containing special copolysealmonofilaments, stabilized copolysters and use of decopoliesters in the manufacture of parameters - Google Patents

Abstract

The present invention relates to paper machine screen containing monofilaments of copolymers with 85 to 99 mol% of the repeating structural unit of formula I and 1 to 15 mol% of the repeating structural unit of formula II, wherein R 1 is a radical of an aliphatic or cycloaliphatic divalent alcohol, or a derivative of mixtures of such alcohols, R 2 represents an aliphatic, cycloaliphatic or mononuclear aromatic dicarboxylic acid radical or derived from mixtures of such dicarboxylic acids, R 3 admits the meanings defined for R 1, and the quantitative indications they refer to the total amounts of the poly

Description

TAMICES FOR PAPERWORK MACHINES. FILTERS AND REINFORCEMENT FABRICS FOR ELASTOMERS. CONTAINING MONOFILAMENTS OF SPECIAL COPOLYSITERS: STABILIZED COPOLYSITERS AND THE USE OF COPOLYSITERS IN THE MANUFACTURE OF TAMPS FOR PAPER MACHINES. FILTERS AND REINFORCEMENT FABRICS FOR ELASTOMEROS The present invention relates to the use of selected copolyesters, containing units of naphthalenedicarbamide acid, in the manufacture of screens for paper machines, filters and reinforcements for elastomers. The copolyesters used are especially suitable for technical applications and have high dimensional stability as well as very good thermal, chemical and anti-hydrolysis resistance. In most cases, mono-filaments for technical applications are subjected to great mechanical stress during use. In addition, in many cases, thermal and chemical stresses must be added, as well as other environmental influences, to which the material must offer sufficient resistance. Faced with all these loads, the material must offer good dimensional stability and constant tensile-elongation properties for the longest possible time of use. An example of technical application, in which a combination of high demands mechanical, thermal and chemical ions, is the use of monofilaments in sieves of paper machines, above all, in the longitudinal sieve, of the pressed heading and of the dry heading. This use requires a monofilament material of high initial modulus and high breaking strength, good resistance to knots and loops, great resistance to abrasion and hydrolysis, in order to withstand the high solitations of the manufacture of the paper and ensure the durability of the sieve. Nowadays, paper machine screens are mainly manufactured with monofilaments made of polyethylene terephthalate in the warp and polyamide-6 or 6.6 in the weft. These sieves may have the disadvantage of expanding (lengthening) in the direction of travel during the life of the sieve in the paper machine and, therefore, may require retensioning. So far there has been no lack of tests to manufacture synthetic monofilament materials, suitable for durable sieves in paper machines. But the demands placed on these technical products are so diverse that only partial solutions to this problem have been possible to date. As an alternative to polyethylene terephthalate, US Pat. No. 5,169,499 describes the use of copolymers based on i, -di and ilolcyclohexane, terephthalic acid and isophthalic acid. These polymers have a good resistance to hydrolysis but comparatively have poor longitudinal strength, at the ends and at the loops.

Other materials such as pol i (phenylene sulfide) also have good resistance to hydrolysis but are expensive to manufacture and also have an initial modulus too low. It is also known to manufacture polyester fibers with very diverse mechanical and textile properties. In particular, by varying the conditions of spinning, stretching and relaxation, monofilaments of polyethylene-phthalate can be manufactured covering a broad spectrum of properties important for technical monofilaments. Until now, the efforts to obtain a monofilament material that simultaneously offers the great dimensional stability, the resistance to abrasion, to the chemical products and to the hydrolysis, that the sieves of the paper machines require, have only given an insuficient result. In the effort to find a polyester fiber that is most suitable for many technical applications, there have also been trials to replace the polyethylene terephthalate by other types of polyester and by copolyesters. Alternative polyesters or polyesters have already been studied, for example, polyethylene naphthalate and copolyesters of 4,4'-biphenyldicarboxylic acids and 2,6-naphthalenedicarboxylic acids, as described, e.g. e.g., in EP-A-202,631, JP-A-73-96,630 and US-A-5,405,6ßA5. Fibers of 4,4'-biphenyldicarboxylic acid and 2-naphthalenedicarboxylic acid were also proposed in W0-A-93 / 02J 22. Thesefibers derived from polyesters with 2,6-naphthalenedicarboxylic acid tend to have a high longitudinal strength and a high modulus if they were spun with high draw without further stretching. The possibility of using the already known materials to produce monofilaments, in particular for making paper machine screens, seems really problematic since, from experience, a high modulus always corresponds to a low resistance to knots and loops. In addition, it is known that polymers with 4,4'-biphenic acid crystallize instantly. For this reason it seems problematic to be able to manufacture monofilaments using this raw material, because a too fast crystallization produces, already during the manufacturing process, an early embrittlement of monafilaments, which consequently break before reaching a sufficient orientation. From JP-A-41-914 there are known monofilaments of poly (ethylene-2,6-naphthalate) suitable for manufacturing fabrics of igrafía. These polymers can be modified with up to 15 mol% of terephthalic or isophthalic acid units. It has now been discovered that, starting from selected copolyesters, monofilaments can be made which are distinguished by a high modulus and better resistance to knots and filaments, which have a chemical stability and a high stability.

Especially good hydrolysis, especially in environments with heat and humidity. These copolymers allow the manufacture of monofilaments of high modulus that can be subjected to great mechanical efforts. An object of the present invention are the sieves for paper machines, filters and reinforcing fabrics for elastomers, containing monofilaments of copolymers with from ñ5 to 99 mol% of the repeating structural unit of the formula I 1 to 15 * molar of the repeating structural unit of formula II -OC-R ^ -CO-O-RS'-O- n), wherein R * is a radical of an aliphatic or cycloaliphatic divalent alcohol, or a derivative of mixtures of such alcohols, Ra represents a radical of an aliphatic, cycloaliphatic or mononuclear aromatic dicarboxylic acid or derived from mixtures of such dicarboxylic acids, Rβ admits the meanings defined for RA, and the quantitative indications refer to the total amounts of the polymer. Copolymers containing 90 to 96 * molar of the repeating structural unit of formula I and 4 to 10 molar% of the repeating structural unit of formula II are preferred. In the case of the dicarboxylic acid component in the repeating structural unit of the formula I, it may be any radical derived from naphthalenedicarboxylic acid, for example from the acids 1,6- 1,4-, 1,5-, 2,7 - and, above all, of 2,6-naphthalenedicarboxylic acid. These radicals can be substituted with one to two inert radicals, for example alkyl or alco? I groups, or halogen atoms. Here, especially preferred are branched or preferably linear alkyl groups of 1 to 6 carbon atoms, most preferably methyl or ethyl, or alkoxy groups of 1 to 6 carbon atoms in the alkyl chain, which may be branched or preferably linear, most preferably methoxy or ethoxy; or chlorine or bromine. When any of these radicals represent groups derived from an aliphatic or cycloaliphatic divalent alcohol, it is any primary, secondary or tertiary divalent alcohol. Preferred aliphatic alcohols have from 2 to 4 carbon atoms. Especially preferred examples among them are 1,3-propanediol, 1,4-butanediol or, above all, 1,2-ethylene glycol. Other examples of the alcohols which can be used in the present invention are polyalkylene glycols, such as di-, tri- or tetra-propylene glycol or di-, tri- or tetra-but i-glycol. These polyalkylene glycols are used especially in small proportion mixed with the corresponding alkylene glycol. Preferred cycloaliphatic alcohols have rings of 6 carbon atoms. A preferred example of them is 1, 4-ciclohe? Andimetanal. These aliphatic or cycloaliphatic alcohol radicals can be substituted with one to two inert radicals. Here, above all, branched or preferably linear alkyl groups of 1 to 6 carbon atoms, most preferably methyl or ethyl, or alkoxy groups of 1 to 6 carbon atoms in the alkyl chain, which may be branched or linear preference, most preferably metaxy or ethoxy; or chlorine or bromine. If any of these groups represents a radical of an aliphatic dicarboxylic acid, it may be linear or branched alkylene radicals, as well as saturated alkylene or ethylenically unsaturated radicals; such radicals have preferably from one to ten carbon atoms. Examples are radicals derived from adipic, sebacic, succinic or fumaric acids. When one of these groups represents a radical of a cycloaliphatic dicarboxylic acid, it is usually a & group with a ring of five or, above all, six carbon atoms; for example 1,4-cyclohexylene. When one of these groups represents a radical of a mononuclear aromatic dicarboxylic acid, it is usually a group with an aromatic ring of six carbon atoms; for example 1,3- or i, 4-f nylene. These aliphatic, cycloaliphatic or aromatic dicarboxylic acid radicals can be substituted with one to two inert radicals. Examples thereof are alkyl or alkoxy groups, or halogen atoms. Here, especially preferred are branched or preferably linear alkyl groups of 1 to 6 carbon atoms, most preferably methyl or ethyl, or alkoxy groups of 1 to 6 carbon atoms in the alkyl chain, which may be branched or with linear preference, very preferably methoxy or eto io either chlorine or bromine. The polysters employed according to the present invention usually have an intrinsic viscosity of at least 0. 5 dl / g, preferably from 0.6 to 1.5 dl / g. The measurement of the intrinsic viscosity is carried out in a solution of the copolyester in dichloroacetic acid at 5 5 ° C. For a series of applications, it is desirable to additionally stabilize the copolyesters used according to the present invention against thermal and / or chemical decomposition. For this purpose, a polyester stabilizer can be added and / or the end groups of the polyester can be masked with agents blockers. In a particularly preferred finishing form, the copolyester employed in the present invention has carboxyl end groups blocked by reaction with a carbodiimide. In another particularly preferred finishing form, the copolyester ester used in the present invention has carboxyl end groups blocked by reaction with carbodiimide, the blocking being carried out mainly with mono- and / or polycarbodiimides, especially with a mixture of and policarbides. For this, 0.4 to 1% by weight of mopo-carbodiimide, preferably from 0.45 to 0.6% by weight, are used. 0. 15 to 2.25% by weight of polycarbodiimide, preferably from 0.75 to 1.6% by weight, based on the amount of polyester. These polyesters with stabilized end groups are known from DE-A-4,30, 392, EP-A-503,421 and EP-A-417, 717. Selected copolyesters, with stabilized end groups, defined above, also they are object of the present invention. The monofilaments used according to the present invention usually have a diameter of 0.1 to 2 mm, preferably between 0.15 and 1 mm. The manufacture of the mono-filaments used according to the present invention. The temperature and the stretching of the spinning, which can be set by adjusting the injection and trailing speeds, as well as the stretching conditions, are selected especially so that the onsfilaments used according to the present invention are obtained with the following properties: Initial module at 25 ° C greater than 12 N / tex, preferably greater than 16 N / tex. Maximum tensile strength referred to the fineness of 30 to 70 Cn / tex, preferably between 40 and 60 Cn / tex. Maximum tensile elongation from 2 to 20%, preferably between 5 and 10%. Resistance to loops of 15 to 40 Cn / tex, preferably between 20 and 35 Cn / te ?. Resistance to knots from 25 to 50 Cp / te ?, preferably between 30 and 45 Cn / te ?. Shrinkage to dry heat at 160 ° C from i to 20%, preferably between 5 and 10%. The fixation of the composition and spinning parameters to achieve a certain combination of properties of the monofilament can be performed routinely by ascertaining for each property in question its dependence on the composition of the polyester and the said spin parameters. In addition to the copolyesters described above, monofilaments used according to the present invention may also contain additives, such as, for example, catalyst residues, auxiliary products of transformation, stabilizers, antioxidants, plasticizers or lubricants. These additives are usually in concentrations of up to 10% by weight, preferably from 0.01 to 5% by weight, especially from 0.1 to 2% by weight. In the case of the catalyst residues, it can be, for example, antimony trioxide or tetraalcoatitanites. As processing aids or lubricants, siloxanes, in particular, dialkyl or polymeric diarylsiloxanes and waxes, as well as organic carboxylic acids with more than 6 carbon atoms and aliphatic, aromatic and / or perfluorinated esters and ethers can be used. The monofilaments may also contain inorganic or organic pigments or matting agents, such as, for example, organic coloring pigments or titanium dioxide, or carbon black as coloring or conductive additive. Examples of stabilizers used are phosphorus compounds, for example phosphoric esters. In another preferred finishing form, the monofilaments used according to the present invention can also contain other polymers, eg extruded fluorinated polymers. The addition of fluorinated polymers in the manufacture of mono-filaments is known, for example, from DE-A-4,307,39. The manufacture of the copolyesters used in the present invention takes place by polycondensation of the corresponding carboxylic acid and diol components, first, for convenience, melt condensing to a median value of the intrinsic viscosity and then in the solid phase to the desired final viscosity. After the solid phase polycondensation, the macromolecular copolyester is spun by melting, in a manner known per se, to obtain monofilaments used according to the present invention. The copolyester is usually dried immediately before spinning, preferably by heating in a dry atmosphere or in a vacuum. The copolyester is then melted in an extruder, passed through a normal spinning filter pack and spun through a spinneret. The meltblown fiber can be cooled in a spin bath (eg water at about 70 ° C) and rolled or stretched at a speed greater than the injection speed of the molten copolyester. For the manufacture of the monofilaments used in the present invention, it has been especially advantageous to work with a melting temperature range of 270 up to 310, preferably between 260 and 300 ° C, and with a drawing degree of 1: 1.5 to 1: 5.0, preferably between 1: 2 and 1: 3. If you work with a higher degree of drafting, the obtained mono and laments are stretched worse and worse and the mechanical properties, especially the resistance to knots and loops, worsen dramatically.

For convenience, the cooling of the spun monofilaments takes place by abrupt cooling in a spin bath. In order for the manufacturing of the mono-laminations of the present invention to be profitable, the driving speed must be from 5 to 30 m / min. , preferably from 10 to 20 m / min. The monofilament thus manufactured can then be subjected to a subsequent stretching, preferably in several steps, especially from two to three stages, with a total draw ratio of 1: 4 to 1: 6, preferably between 1: 5 and 1: 7, and then can be heat-set at temperatures of 190 to 250 ° C, preferably between 200 and 220 ° C, working at a constant length or allowing a shrinkage of 2 to 10%, preferably from 3 to 6%. Another object of the present invention is the use of these fibers to manufacture paper machine screens, filters or reinforcing fabrics for elastomers. To manufacture paper machine screens, monofilaments can be woven on wide automatic looms, with the usual machine parameters when weaving polyethylene terephthalate. For example, a good fabric is obtained by weaving monofilaments of 0.17 mm in diameter in the warp with an upper weft of 0.2 mm and a lower weft of 0.22 mm. The fabric has very good dimensional stability and resistance to abrasion, which can still be improved by using monofilaments of polyamide in the lower plot. The obtained tfejido usually receives a later treatment in a device of ter ation a correspondingly di passion, in order to adjust the specific properties of the sieve that requires each case. Compared to the material made with ordinary monolayers of polyethylene lerephthalate, the tissue of papermaking machines thus produced with the monofilaments used in the present invention has better dimensional stability in the warp and weft direction, and thus is achieved a smoother and faster gear in the machine, which favors the quality and performance of the paper obtained. The fabrics manufactured starting from the mono-filaments of the present invention can be used as filtering material of excellent mechanical and chemical stability or as a very resistant and dimensionally stable reinforcement fabric for conveyor belts. The following examples clarify the present invention without limiting it.

EXAMPLE 1 A copolyester obtained by reaction of 92 mol% of 2,6-dimethyl naphthalenedicarboxylate and 6 mol% of dimethyl terephthalate and ethylene glycol is spun at a mass temperature of 300 ° C. The monof i laments thus obtained, after cooling sharply in a spin bath at 70 ° C, they are stretched at a ratio of 1: 6.0. Monofilaments with the following properties are obtained: Diameter: 0.17 mm Resistance to breakage: 55 Cn / tex Elongation at break: 10.5% Module: 16 N / tex Resistance to knots: 25 Cn / tex Resistance to loops: 29 Cn / tex EXAMPLE 2 A mono-lamento manufactured analogously to Example 1 with a diameter of 0.5 mm presents, after 60 hours of treatment with saturated steam at 135 ° C, a resistance at break of 52%. By adding carbodi imides, the remaining strength at break exceeds 90%. On the other hand, a monofilament of stabilized polyterephthalate with can carbides has a residual strength at break of 35%.

Claims (7)

NOVELTY OF THE INVENTION CLAIMS

1. - Paper machine screen containing monofilaments of copolymers with 65 to 99 mol% of the repeating structural unit of formula I 1 to 15 mol% of the repeated structural unit of formula II -OC-Ra-CO-O-R »-0- (II), where Rx is a radical of an aliphatic or cycloaliphatic divalent alcohol, or a derivative of mixtures of such alcohols, Ra represents a radical of an aliphatic, cycloaliphatic or aromatic mononuclear dicarboxylic acid or derived from mixtures of such dicarboxylic acids, R "admits the meanings defined for Rx, and the quantitative indications refer to the total amounts of the polymer

2. Paper machine screen according to claim 1, characterized in that the cspolymer contains from 90 to 96 mol% of the repeated structural unit. of the formula I and from 4 to 10 mol% of the repeated structural unit of formula II.

3. Paper machine screen according to claim 1, characterized in that the dicarboxylic acid component in the repeated structural unit of the formula I is derived from the 2,6-naphthalenedicarboxylic acid.

4. Paper machine screen according to claim 1, characterized in that Rx and / or Ra are derivatives of 1,3-propanediol, 1,4-butanediol or, above all, 1,2-ethylene glycol.

5. Paper machine screen according to claim 1, characterized in that R and / or Rβ are derived from 1,4-cyclohexane and ethanol.

6. Paper machine screen according to claim 1, characterized in that Ra is a derivative of terephthalic acid and / or isophthalic acid.

7. Paper machine screen according to claim 1, characterized in that the monofilaments contain, at least, another extrudable polymer, preferably an extrudable fluorinated polymer. 6.- Filter containing monofilaments of copolymers with 65 to 99 mol% of the repeated structural unit of the formula I 1 to 15 mol% of the repeated structural unit of formula II -OC-Ra-CO-O-R3-0- (II, where Rx is a radical of an aliphatic or cycloaliphatic divalent alcohol, or a derivative of mixtures of such alcohols, Ra represents a radical of an aliphatic, cycloaliphatic or aromatic dicarboxylic acid mannonated or derived from mixtures of such dicarboxylic acids, R admits the meanings defined for R, and the quantitative indications refer to the total amounts of the polymer. 9. Filter according to claim 6, characterized in that the copolymer contains from 90 to 96 mol% of the repeating structural unit of formula I and from 4 to 10 mol% of the repeating structural unit of formula II. 10. Filter according to claim 6, characterized in that the dicarboxylic acid component in the repeated structural unit of formula I is derived from 2,6-naphthalenedicarboxylic acid. 11. Filter according to claim 6, characterized because R and / or Ra are derivatives of 1,3-pro-anodiol, 1,4-butanediol or, especially, of 1,2-ethylene glycol. 12. Filter according to claim 6, characterized in that Rx and / or R3 are derivatives of 1,4-cyclohexamethanol. 13. Filter according to claim 6, characterized in that Ra is a derivative of terephthalic acid and / or isophthalic acid. 14. Filter according to claim 1, characterized in that the monofilaments contain, at least, another extrudable polymer, preferably an extrudable fluorinated polymer. 15.- Fabric for elastomer reinforcement containing monofilaments of copolymers with 65 to 99 mol% of the repeating structural unit of the formula I 1 to 15 mol% of the repeated structural unit of formula II -OC-Ra-CO-O-Rta-O- (II) where RA is a radical of an aliphatic or cycloaliphatic divalent alcohol, or a derivative of mixtures of such alcohols, Ra represents a radical of an aliphatic, cycloal ifatic or mononuclear aromatic dicarboxylic acid or is derived from mixtures of such dicarboxylic acids, R3 * admits the meanings defined for RA, and the quantitative indications refer to the total amounts of the polymer. 16.- Fabric for reinforcement of elastomers according to claim 15, characterized in that the copolymer contains from 90 to 96 mol% of the repeated structural unit of the formula I and from 4 to 10 mol% of the repeated structural unit of the formula II. 17.- Fabric for reinforcement of elastomers according to claim 15, characterized in that the dicarboxylic acid component in the repeated structural unit of the formula I is derived from the 2,6-naphthalenedicarboxylic acid. 16.- Fabric for reinforcement of elastomers according to the rei indication 15, characterized in that R * and / or R3 are derivatives of 1,3-propanediol, 1,4-butanediol or, above all, 1,2-ethylene glycol. 19.- Fabric for reinforcement of elastomers according to claim 15, characterized in that RA and / or R3 are derivatives of 1,4-cyclohexanedimethanol. 20.- Fabric for reinforcement of elastomers according to the rei indication 15, characterized in that Ra is a derivative of terephthalic acid and / or isophthalic acid. 21.- Fabric for reinforcement of elastomers according to claim 15, characterized in that the monofilaments they contain. at least one other extrudable polymer, preferably an extrudable fluorinated polymer. 22. Copolymer containing 65 to 99 mol% of the repeating structural unit of the formula I 1 to 15 mol% of the repeated structural unit of formula II -OC-Ra-CO-0-R »-0- (II, where Rx is a radical of an aliphatic or cycloaliphatic divalent alcohol, or a derivative of mixtures of such alcohols, Ra represents a radical of an aliphatic, cycloaliphatic or aromatic monoanucleated dicarboxylic acid or derived from mixtures of such dicarboxylic acids, R3 admits the meanings defined for RA, and the quantitative indications refer to the total amounts of the polymer, characterized in that the terminal groups of this copolymer are stabilized with a blocker, preferably with a carbodiimide. 23. Copolymer according to claim 22, characterized in that it is stabilized by reaction with a mono and / or a polycarbodiimide, preferably with a combination of mono- and poly-carbodiimide. 24. Use of monofilaments according to claim 1 to manufacture paper machine screens. 25. Use of the monofilaments according to claim 6 to manufacture filters. 26. Use of the monofilaments according to claim 16 to manufacture reinforcing fabrics for elastomers.